1. Field of the Invention
This invention generally relates to a motorized bicycle derailleur. More specifically, the present invention relates to a motorized bicycle derailleur assembly in which a chain guide has a range of movement between its top and low gear positions that is smaller than a range of movement outputted by a motor unit driving the chain guide between its top and low gear positions.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. In fact, bicycles have recently been equipped with electrical components to make riding easier and more enjoyable for the rider. Some bicycles are equipped with automatic shifting units that are automatically adjusted according to the riding conditions by a cycle computer or control unit. In particular, the front and rear derailleurs have recently been automated.
Generally speaking, the front derailleur is secured to the seat tube of the bicycle frame or the bottom bracket, while the rear derailleur is secured to the rear triangle of the frame. In either case, a derailleur includes a fixed or base member non-movably secured to a bicycle frame, and a movable member supported to be movable relative to the fixed member via a linkage. The movable member typically has a chain guide with a pair of cage plates for moving a chain between the front or rear sprockets. The movable member is usually biased in a given direction relative to the fixed member by a spring. The movable member is usually moved relative to the fixed member by pulling and/or releasing a shift control cable that is coupled to the respective derailleur. In a manually operated derailleur, a control cable is connected to one of the pivotal links to apply a torque thereto, thereby causing the links to move the movable member. The control cable is fixed to the link in a position such that an operating force applied to the control cable is converted into a link swinging torque. The movement of the control cable is typically controlled by a shift operating device that has one or more levers, a winding member and in indexing mechanism in a conventional manner.
In recent years, derailleurs have been motorized. In a motorized derailleur, a motor is typically used to pull and release a control cable to move the movable member, or the motor is connected by a drive train (transmission) to the derailleur without a conventional control cable to move the movable member. In either case, the motor is typically an electric motor that is operatively coupled to a control unit. The control unit can automatically control the motor, and thus, automatically control movement of the movable member of the derailleur. Alternatively, electrical shift buttons can be provided, which are operatively coupled to the control unit such that the rider can control the shifting of the derailleur.
While these prior motorized derailleurs work relatively well, they do suffer from some deficiencies. In particular, one problem with these prior motorized derailleurs is that a drive motor is provided with a range of movement that does not match a range of movement of the chain guide between its top and low gear positions. This can result in an overcurrent in the motor, which can reduce the motor life as well as waste electrical power.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved motorized bicycle derailleur assembly. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.